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Copyright of China Petroleum Machinery is the property of China Petroleum Machinery Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A series of CaF2-Al2O3-TiO2 welding fluxes with TiO2 content from 20 to 60 wt.% were applied to join EH36 shipbuilding steel under high heat input submerged arc welding. The effect of TiO2 content on Charpy impact energy, inclusion characteristics, microstructure features, and chemical compositions of weld metals were systematically investigated. A maximum Charpy impact energy of 81.67 J was detected for the weld metal treated by the flux with 50 wt.% TiO2. Such unusual behavior was consistent with the initially increased and subsequently decreased changing trend for the faction of acicular ferrite, which is closely related to the formation, number density, and size distribution of significantly populated TiO2-containing inclusions that were largely dictated by the transfer of O and Ti. Current findings may serve as a viable way of tuning weld metal properties enabled by optimized flux designs. [ABSTRACT FROM AUTHOR]

Copyright of Erzincan University Journal of Science & Technology is the property of Erzincan Binali Yildirim Universitesi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ductile-to-brittle transition (DBT) characteristics of three steels for reactor pressure vessel (RPV) belt line application are analyzed from new parameters based on model functions describing the strength and toughness characteristics of the materials. In order to estimate nil-ductility temperature (NDT) from strength property, a strain rate-compensated temperature parameter based on the thermally activated deformation of materials is adopted. A measure of NDT is determined from tensile strength properties for the first time assuming an estimated notch tip strain rate at the lower shelf. It is estimated to be 110, 42, and 106 K for the Cr-Mo-V-Ni, 20MnMoNi55, and A533B steels, respectively. The measure of ductile-to-brittle transition temperature (DBTT) in steels using 41-J Charpy impact-absorbed energy on the basis of a logistic class of functions is compared and shown to be equivalent with those obtained from fitting the tanh model equation. A bi-logistic function based on the concept of separable parameters representing the fracture of ductile and brittle zones in steels within the DBTT regime was applied to model the Charpy impact energy behavior of the three steels. The bi-logistic function-fitting parameters yielded a new measure of brittleness as a DBT characteristic of steels that correlated well with other measures of transition temperature of the selected RPV steels. The parameters from the hyperbolic and logistic fitting were used to develop a model relationship suitable for the generation of a master curve based on Charpy energy in exponential form that unifies the transition temperature behavior of the selected western and eastern RPV materials. The model relationship is also found to closely predict ~5 K of the reference temperature To determined as per American Society for Testing and Materials standard E1921 of the selected RPV steels. [ABSTRACT FROM AUTHOR]

Fe-30Mn-0.05C steel specimens with cold-rolled, partially recrystallized, fine-grained, and coarse-grained microstructures were fabricated by means of 80% cold rolling followed by annealing at 550–1000 °C. The initial and deformed microstructures were characterized, and the Charpy impact properties were tested at room temperature (RT) and liquid nitrogen temperature (LNT). It was found that the Charpy absorbed energy increased with the annealing temperature, while the specimens showed different trends: parabolic increase at RT and exponential increase at LNT, respectively. Compared with the fully recrystallized specimens, those with a partially recrystallized microstructure exhibited lower impact energy, especially at LNT. This was because cracks tended to nucleate and propagate along the recovery microstructure where stress concentration existed. The grain size played an important role in the twinning behavior and impact properties. High Charpy impact energy (~320 J) was obtained in the coarse-grained specimen having the grain size of 42.1 μm at both RT and LNT, which was attributed to the activation of high-density deformation twinning. However, deformation twinning was inhibited in the specimen with the average grain size of 3.1 μm, resulting in limited work hardening and lower impact energy. [ABSTRACT FROM AUTHOR]

The number of additive manufacturing methods and materials is growing rapidly, leaving gaps in the knowledge of specific material properties. A relatively recent addition is the metal-filled filament to be printed similarly to the fused filament fabrication (FFF) technology used for plastic materials, but with additional debinding and sintering steps. While tensile, bending, and shear properties of metals manufactured this way have been studied thoroughly, their fatigue properties remain unexplored. Thus, the paper aims to determine the tensile, fatigue, and impact strengths of Markforged 17-4 PH and BASF Ultrafuse 316L stainless steel to answer whether the metal FFF can be used for structural parts safely with the current state of technology. They are compared to two 316L variants manufactured via selective laser melting (SLM) and literature results. For extrusion-based additive manufacturing methods, a significant decrease in tensile and fatigue strength is observed compared to specimens manufactured via SLM. Defects created during the extrusion and by the pathing scheme, causing a rough surface and internal voids to act as local stress risers, handle the strength decrease. The findings cast doubt on whether the metal FFF technique can be safely used for structural components; therefore, further developments are needed to reduce internal material defects. [ABSTRACT FROM AUTHOR]

• The lining plate of SAG is made toughness by controlling the tempering process while maintaining its strength. • The concurrent study of V-notch and U-notch achieved the optimal heat treatment process. • The low-density GNDs and high content of blocks improved the toughness. The microstructure evolution and strength-toughness matching relationship of advanced ultra-high strength steel were studied under the tempering temperature range of 200–400 °C. The Charpy impact absorption energy of U-notch and V-notch focused on the crack initiation and crack propagation processes, respectively. The peak impact absorption energy of the U-notch appeared at 300 °C due to reduced stress concentration from low GND (Geometrically Necessary Dislocations) density. The optimal mechanical properties were found after tempering at 250 °C, where martensitic blocks hindered crack propagation, resulting in the peak impact energy of V-notch. [ABSTRACT FROM AUTHOR]

Welding is used as the main joining method in various industries, including the shipbuilding industry. In the case of welded structures, structural integrity assessment is essential to ensure the safety of the structure because many defects inevitably exist during the manufacturing process. The value of reliable fracture toughness is required for structural integrity assessment. It is obtained by the fracture toughness test, but the fracture toughness test requires a lot of time and effort. Therefore, many studies have been conducted on efficient methods to evaluate fracture toughness. Among the various studies that estimate fracture toughness, some have been conducted using the Charpy impact test, which is relatively simple compared to the fracture toughness test. This study conducted a series of experimental investigations on API 2W Gr.50 steel applied with different welding conditions. Based on the Charpy impact test results, the fracture behavior was well estimated in the ductile to brittle transition region according to the temperature. However, there was a difference in the accuracy of predicting fracture behavior depending on the welding process. Therefore, additional consideration reflecting the various welding conditions is required to ensure the safety of welded structures. [ABSTRACT FROM AUTHOR]

This paper aims to study the relationship between the microstructure and the mechanical properties of X70 submarine pipeline steel with 40.5 mm thickness. The microstructure was examined by using optical microscopy, scanning electron microscopy and an electron backscattered diffractometer, while the mechanical properties were examined by using a hardness test, a tensile test, a Charpy impact test and a drop weight tear test (DWTT), respectively. The results show that the base metal (BM) of the pipe has a low yield ratio of 0.83 and an excellent elongation of more than 45%. The DWTT shear area of the steel plate reaches 87%, showing excellent low-temperature toughness. The Charpy impact energy increases when the distance from the fusion line increases, and it reaches a maximum at the BM near the heat-affected zone (HAZ) due to the small martensite-austenite (MA) constituents and fine grains. The concentrated distribution of blocky/slender MA constituents along the prior austenite grain boundaries of the intercritically reheated coarse-grained HAZ and the large MA constituents are the main reasons for the deteriorating impact toughness. Delamination cracks in the DWTT fracture surface only occurred in the midthickness of a sample with a small opening width that spread about 2.1 mm perpendicular to the DWTT fracture surface and were finally arrested at the acicular ferrite clusters containing a high density of high-angle boundaries. [ABSTRACT FROM AUTHOR]

To address the design difficulty of 1 422 mm×1 219 mm tee used at stations along China–Russia Eastern Gas Pipeline under low temperature condition, the domestic and foreign pipe fitting standards were compared, and similar projects were investigated. A comprehensive study was carried out from the determination of design temperature, selection of materials, design of structural dimensions, establishment of Charpy impact toughness, etc., revealing that the minimum design temperature of fittings in the China–Russia Eastern Gas Pipeline is -45 ℃, and the material of tee is X80. The limit analysis design method in Specification for high-test wrought butt-welding fittings (SY/T 0609-2016), is used to determine that the original thickness of the tee is 57 mm, and the length from the end of the tee branch pipe to the center line of main pipe is 1 090 mm. The Charpy impact test temperature is determined to be -45 ℃. The mean Charpy impact energy of tee weld and heat affected zone is not less than 50 J, and that of pipe body is not less than 60 J. The determination of technical indexes would serve as a basis for the formulation of technical conditions for the manufacture of tees at stations along China–Russia Eastern Gas Pipeline under low temperature condition. The design and manufacture of the new product has reached advanced level in the world.

Fe-30Mn-0.05C steel specimens with cold-rolled, partially recrystallized, fine-grained, and coarse-grained microstructures were fabricated by means of 80% cold rolling followed by annealing at 550–1000 °C. The initial and deformed microstructures were characterized, and the Charpy impact properties were tested at room temperature (RT) and liquid nitrogen temperature (LNT). It was found that the Charpy absorbed energy increased with the annealing temperature, while the specimens showed different trends: parabolic increase at RT and exponential increase at LNT, respectively. Compared with the fully recrystallized specimens, those with a partially recrystallized microstructure exhibited lower impact energy, especially at LNT. This was because cracks tended to nucleate and propagate along the recovery microstructure where stress concentration existed. The grain size played an important role in the twinning behavior and impact properties. High Charpy impact energy (~320 J) was obtained in the coarse-grained specimen having the grain size of 42.1 μm at both RT and LNT, which was attributed to the activation of high-density deformation twinning. However, deformation twinning was inhibited in the specimen with the average grain size of 3.1 μm, resulting in limited work hardening and lower impact energy.

This study investigates the Fe50Mn30Co10Cr10 high entropy alloy (HEA), featuring a dual-phase structure with face-centered cubic (FCC) and hexagonal close-packed (HCP) phases, in both cast and forged states. The cast samples exhibited an average tensile strength of 675.9 MPa and an elongation at break of 34 %, while the forged samples showed superior properties with a strength of 821.0 MPa and 50 % elongation. Impact tests at room temperature, 200 K, and 77 K revealed that forged samples consistently had higher impact energy (144 J, 119 J, and 109 J, respectively) compared to cast samples (99 J, 80 J, and 66 J). This research underscores the significant influence of the dual-phase structure and fabrication process on the mechanical and impact properties of the Fe50Mn30Co10Cr10 system HEAs. • Forging enhances the dual-phase structure of Fe50Mn30Co10Cr10 HEAs, leading to improved mechanical strength and ductility. • Microstructural engineering through grain refinement elevates the resistance to impact. • Fe50Mn30Co10Cr10 HEA shows no distinct ductile-to-brittle transition from room temperature to 77K. [ABSTRACT FROM AUTHOR]

Modern construction must meet the function for which it has been made and must be safe and economical to operate. In order to achieve the foregoing, the design of the structure should strive for an optimal solution. Such a design is usually based on the optimal choice of material and the optimal dimensions of structural elements. In order to select the optimal material for the manufacture of structural elements, it is necessary to have data on the behavior of the material in the intended operating conditions. In this sense, this paper deals with experimental research and analysis of the behavior of several types of materials subjected to approximately the same operating conditions. Under considerations were low-alloy structural steel (1.7225), special structural steel (1.7147), alloy carbon steel (1.5920), and alloy stainless steel (1.4034). The mechanical behavior of the tested materials, in terms of monitoring changes and mutual comparisons of mechanical properties, is shown on the basis of engineering stress–strain diagrams, while their creep resistances are monitored and compared with each other based on creep curves. As for the fracture toughness, it can be estimated based on the results of the fracture impact energy test, applying the known calculation method. In accordance with the tests performed at room temperature, the following results related to the maximum ultimate tensile strength ( σ m /MPa), Charpy V-notch impact energy (CVN /J), and fatigue limit ( σ f / MPa) at stress ratio R , are shown as follows: [Mat. Nr. σ m / MPa ; CVN / J ; σ f , R / MPa 20 , and their magnitudes are : 1.7225 733 ; 166 ; 532 0.25 20 ; 1.7147 560 ; 178 ; − 20 ; 1.5920 612 ; 220 ; 285 − 1 20 ; 1.4034 782 ; 8 ; 325 − 1 20 . [ABSTRACT FROM AUTHOR]

Welding is used as the main joining method in various industries, including the shipbuilding industry. In the case of welded structures, structural integrity assessment is essential to ensure the safety of the structure because many defects inevitably exist during the manufacturing process. The value of reliable fracture toughness is required for structural integrity assessment. It is obtained by the fracture toughness test, but the fracture toughness test requires a lot of time and effort. Therefore, many studies have been conducted on efficient methods to evaluate fracture toughness. Among the various studies that estimate fracture toughness, some have been conducted using the Charpy impact test, which is relatively simple compared to the fracture toughness test. This study conducted a series of experimental investigations on API 2W Gr.50 steel applied with different welding conditions. Based on the Charpy impact test results, the fracture behavior was well estimated in the ductile to brittle transition region according to the temperature. However, there was a difference in the accuracy of predicting fracture behavior depending on the welding process. Therefore, additional consideration reflecting the various welding conditions is required to ensure the safety of welded structures.

This paper aims to study the relationship between the microstructure and the mechanical properties of X70 submarine pipeline steel with 40.5 mm thickness. The microstructure was examined by using optical microscopy, scanning electron microscopy and an electron backscattered diffractometer, while the mechanical properties were examined by using a hardness test, a tensile test, a Charpy impact test and a drop weight tear test (DWTT), respectively. The results show that the base metal (BM) of the pipe has a low yield ratio of 0.83 and an excellent elongation of more than 45%. The DWTT shear area of the steel plate reaches 87%, showing excellent low-temperature toughness. The Charpy impact energy increases when the distance from the fusion line increases, and it reaches a maximum at the BM near the heat-affected zone (HAZ) due to the small martensite-austenite (MA) constituents and fine grains. The concentrated distribution of blocky/slender MA constituents along the prior austenite grain boundaries of the intercritically reheated coarse-grained HAZ and the large MA constituents are the main reasons for the deteriorating impact toughness. Delamination cracks in the DWTT fracture surface only occurred in the midthickness of a sample with a small opening width that spread about 2.1 mm perpendicular to the DWTT fracture surface and were finally arrested at the acicular ferrite clusters containing a high density of high-angle boundaries.

[Display omitted] • A size-independent instrumented spherical indentation test (ISIT) to predict fracture toughness of wheel steels. • Correlate fracture toughness and Charpy impact energy (CVN) of wheel steels by ISIT. • An alternative representative stress–strain method to predict tensile properties by ISIT. • Rapid evaluation of trade-offs between yield strength and CVN of wheel steels under various cooling rates. In this paper, an improved size-independent instrumented spherical indentation test (ISIT) method was proposed to determine tensile strength and fracture toughness on wheel rims of two different types of wheel steels. Additionally, Charpy impact specimens were taken from three specific positions on the wheel rims and subjected to standard Charpy impact testing. The resulting Charpy impact energy (CVN) were matched with the fracture toughness measured by ISIT (K Ic,IT) at the same positions. There was a clear linear correlation between CVN and the square of K Ic,IT , which was consistent with the established relationship between both properties as determined by conventional Charpy impact and compact tension tests. Therefore, we expanded the ISIT method to study the impact of cooling rates on the variation of yield strength and Charpy impact energy across the wheel rim. To accomplish this, we designated additional testing points on the wheel rim using the ISIT method. The investigation found trade-offs between strength and impact toughness of wheel steels under different cooling rates. The above findings demonstrated the effectiveness of using the ISIT method, which facilitated high-resolution fracture toughness measurement, to establish accurate correlation between CVN and fracture toughness of wheel steels. Moreover, this ISIT method can be employed to regulate heat treatment of material properties to meet specific application requirements. [ABSTRACT FROM AUTHOR]

To achieve high strength and high impact toughness, three kinds of bimodal microstructure of Ti–6Al–4V-0.5Mo-0.5Zr alloy pipe were tailored through solution treatment at the α+β phase region (860 °C, 890 °C, and 920 °C) and followed by aging at 500 °C. The bimodal microstructure consists of the primary α (α p) and β-transformed domain (β t), in which the secondary α phase (α s) precipitated in the β matrix, with different volume fraction. With the increase in solution temperature, the grain size of α p remained unchanged while the volume fraction decreased. At the same time, the volume fraction of β t and the width of α s phase increased. Furthermore, the content of low-angle grain boundaries inside the α p phase decreased. Subsequent aging resulted in finer precipitation of α s within the β t domain. Solution treatment at 890 °C and ageing at 500 °C (denoted as the STA890 sample) achieved an excellent combination of yield strength 903 MPa, tensile strength 1023 MPa, elongation 12.9%, and impact energy 31 J. With the increase of α s width, the strength of the alloy decreased, and the ductility increased slightly. Higher impact energy originated from {10 1 ‾ 2} tension twins activated in the STA890 sample during the impact loading process, α p and β t underwent severe bending and plastic deformation. The present study provides a feasible industrial heat treatment strategy for improving impact energy with high strength of the α+β titanium alloy pipe used for oil drilling. [ABSTRACT FROM AUTHOR]

In this paper, uniaxial material properties, creep resistance and impact energy of the austenitic heat-resistant steel (1.4841) are experimentally determined and analysed. Engineering stress–strain diagrams and uniaxial short-time creep curves are examined with computer-controlled testing machine. Impact energy has been determined and fracture toughness assessed. Investigated data are shown in the form of curves related to ultimate tensile strength, yield strength, modulus of elasticity and creep resistance. All of these experimentally obtained results are analysed and may be used in the design process of the structure where considered material is intended to be applied. Based on these results, considered material may be classified as material of high tensile strength (688 MPa/293 K; 326 MPa/923 K) and high yield strength (498 MPa/293 K; 283 MPa/923 K) as well as satisfactory creep resistance (temperature/stress →$ \to $strain (%) at 1,200 min: 823 K/167 MPa →$ \to $0.25 %; 923 K/85 MPa →$ \to $0.2 %).

In the present study, the Charpy impact energy of ferritic and austenitic functionally graded steel produced by electroslag remelting has been modeled in crack divider configuration. To produce functionally graded steels, two slices of plain carbon steel and austenitic stainless steels were spot welded and used as electroslag remelting electrode. Functionally graded steel containing graded layers of ferrite and austenite may be fabricated via diffusion of alloying elements during remelting stage. Vickers microhardness profile of the specimen has been obtained experimentally and modeled with artificial neural networks. To build the model for graded ferritic and austenitic steels, training, testing and validation using respectively 174 and 120 experimental data were conducted. A good fit equation that correlates the Vickers microhardness of each layer to its corresponding chemical composition was achieved by the optimized network for both ferritic and austenitic graded steels. Afterward, the Vickers microhardness of each layer in functionally graded steels was related to the Charpy impact energy of the corresponding layer. Finally, by applying the rule of mixtures, Charpy impact energy of functionally graded steels in crack divider configuration was found through numerical method. The obtained results from the proposed model are in good agreement with those acquired from the experiments. [ABSTRACT FROM AUTHOR]

Cast stainless steels used in nuclear power plants suffer from fracture toughness losses owing to thermal aging after long-term service at temperatures ranging from 280-320°C. To study the thermal aging embrittlement of Z3CN20.09M duplex stainless steel produced in China, accelerated thermal aging experiments were carried out at 350, 380, and 400°C for up to 10000 h. Microhardness and Charpy impact energies were measured at different aging times. The microhardness of ferrite increased drastically over the initial aging time of 2000 h at 380 and 400°C and then slowly reached HV0.01 560. In contrast to this observed change in microhardness, Charpy impact energies sharply decreased after initial aging and then gradually reached a minimum value. Taking the microhardness of the ferrite phase as the parameter describing the thermal kinetics of the stainless steel samples, the activation energy of thermal aging was calculated to be 51 kJ/mol. Correlations between the thermal aging parameter, P, and ferrite microhardness and between P and Charpy impact energy were also analyzed. The results showed that the activation energy calculated from the ferrite microhardness is much more reasonable than that obtained using other parameters, such as chemical composition and impact energy. [ABSTRACT FROM AUTHOR]

The use of a material for a particular purpose is based on its properties. In this sense, the article deals with the analysis of the results of experimental researches performed on steel 51CrV4. Experimental studies included responses of material at room and high temperatures as well as creep and fatigue behaviors of considered material. Responses of the material at room and high temperatures are displayed in the form of engineering stress-strain diagrams. Based on these responses were determined mechanical properties such as ultimate tensile strength (770 MPa/20 °C; 98 MPa/700 °C), 0.2 offset yield strength (642 MPa/20 °C; 60 MPa/700 °C) and modulus of elasticity (198 GPa/20 °C; 37 GPa/700 °C). Short time creep curves show the behavior of material at certain high temperatures and stress strevels. Each creep process is performed at constant temperature and the corresponding constant stress. Charpy impact energy (average values: 20 J/20 °C; 65 J/200 °C) was tested at different temperatures, and consequently, fracture toughness was calculated based on these results. Finally, uniaxial fatigue limit in amount of 251 MPa was calculated based on uniaxial high cycle fatigue tests at stress ratio of R  =  − 1. [ABSTRACT FROM AUTHOR]

To study the thermal aging embrittlement of Z3CN20.09M duplex stainless steel produced in China, accelerated thermal aging experiments were carried out at 380 °C up to 9000 h. Microhardness measurements, Charpy impact and eddy current tests were performed on aged samples to characterize their thermal aging embrittlement. The results showed that the signal amplitude of eddy current decreased with the increase in aging time. Two quantitative correlations of the eddy current signal amplitude with both the Charpy impact energy, and the Vickers microhardness of the ferrite phase are obtained. The study showed that eddy current testing could be used to non-destructively evaluate the thermal aging embrittlement of cast duplex stainless steels. [ABSTRACT FROM AUTHOR]

The present study was carried out on 2017A aluminium alloy, in order to determine the influence of heat treatments on the fracture toughness determined by three point bending tests and empirical formula correlations used Charpy impact energy. The three point bending test has shown that the minimum values of fracture toughness and maximum load were found in the annealed state. Moreover, the hardening heat treatment increases them considerably, especially in the artificially aged condition of the alloy where it provided the maximum values. Schindler’s empirical formula gave the best estimation of fracture toughness in all metallurgical states of 2017A aluminium alloy. [ABSTRACT FROM AUTHOR]

The paper presents and analyzes the experimental results of the effect of elevated temperatures on the engineering properties of steel 42CrMo4. Experimental data relating to the mechanical properties of the material, the creep resistance as well as Charpy impact energy. Temperature dependence of the mentioned properties is also shown. Some of creep curves were simulated using rheological models and an analytical equation. Finally, an assessment of fracture toughness was made that was based on experimentally determined Charpy impact energy. Based on the obtained results it is visible that the tensile strength (617 MPa) and yield strength (415 MPa) have the highest value at the room temperature while at the temperature of 700 °C (973 K) these values significantly decrease. This steel can be considered resistant to creep at 400 °C (673 K), but at higher temperatures this steel can be subjected to low levels of stress in a shorter time.

Hot press forming (HPF) steel sheets are austenitized, press-formed, and rapidly cooled to obtain a martensitic microstructure with an ultra-high strength. When they are insufficiently austenitized, their microstructures might contain a small amount of untransformed ferrite, which can deteriorate impact toughness as well as strength, but its causes and relevant fracture mechanisms have not been clearly verified yet. In this study, thus, 1.8-GPa-grade HPF sheets were austenitized at various temperature and time, and their tensile and Charpy impact test results were analyzed in relation with untransformed ferrite and its effect on fracture mechanisms. In the HPF sheets containing the untransformed ferrite, voids were formed mostly at ferrite/martensite interfaces, and were grown and propagated linearly to form a cleavage crack, whereas deformation bands were well developed without voids or cracks in the non-ferrite-containing sheets. The highly localized strains accommodated in the soft ferrite made ferrite/martensite interfaces or ferrite itself work as fracture initiation sites, which led to the brittle fracture and consequently to the deterioration of impact energy. This result can provide an important idea for optimization of austenitization conditions demanded for ultra-high strength and excellent impact toughness in HPF applications. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study that examines variations of Charpy impact energy of a welded steel plate, depending upon the welding method and the method for obtaining the Charpy specimens. Flux cored arc welding (FCAW) and Gas tungsten arc welding (GTAW) were employed to weld an SA516 Gr. 70 steel plate. The methods of wire cutting and water-jet cutting were adopted to take samples from the welded plate. The samples were machined according to the recommendations of ASTM SEC. II SA370, in order to fit the specimen dimension that the Charpy impact test requires. An X-ray diffraction (XRD) method was used to measure the as-weld residual stress and its redistribution after the samples were cut. The Charpy impact energy of specimens was considerably dependent on the cutting methods and locations in the welded plate where the specimens were taken. The specimens that were cut by water jet followed by FCAW have the greatest resistance-to-fracture (Charpy impact energy). Regardless of which welding method was used, redistributed transverse residual stress becomes compressive when the specimens are prepared using water-jet cutting. Meanwhile, redistributed transverse residual stress becomes tensile when the specimens are prepared using wire cutting. [ABSTRACT FROM AUTHOR]

Surveillance samples of a low copper (nominally 0.05 wt.% Cu) forging and a higher copper (0.23 wt.% Cu) submerged arc weld from the R. E. Ginna reactor pressure vessel have been characterized by atom probe tomography (APT) after exposure to three levels of neutron irradiation, i.e., fluences of 1.7, 3.6 and 5.8 × 10 23 n.m −2 (E > 1 MeV), and inlet temperatures of ∼289 °C (∼552 °F). As no copper-enriched precipitates were observed in the low copper forging, and the measured copper content in the ferrite matrix was 0.04± <0.01 at.% Cu, after neutron irradiation to a fluence of 1.7 × 10 23 n.m −3 , this copper level was below the solubility limit. A number density of 2 × 10 22 m −3 of Ni–, Mn– Si-enriched precipitates with an equivalent radius of gyration of 1.7 ± 0.4 nm were detected in the sample. However, Cu-, Ni-, Mn-enriched precipitates were observed in specimens cut from different surveillance specimens from the same forging material in which the overall measured copper level was 0.08± <0.01 at.% (fluence of 3.6 × 10 23 n.m −3 ) and 0.09± <0.01 at.% Cu (fluence of 5.8 × 10 23 n.m −3 ). Therefore, these slightly higher copper contents were above the solubility limit of Cu under these irradiation conditions. A best fit of all the composition data indicated that the size and number density of the Cu-enriched precipitates increased slightly in both size and number density by additional exposure to neutron irradiation. High number densities of Cu-enriched precipitates were observed in the higher Cu submerged arc weld for all irradiated conditions. The size and number density of the precipitates in the welds were higher than in the same fluence forgings. Some Cu-enriched precipitates were found to have Ni-, Mn- Si-, and P-enriched regions on their surfaces suggesting a preferential nucleation site. Atom maps revealed P, Ni, and Mn segregation to, and preferential precipitation of, Cu-enriched precipitates over the surface of a grain boundary in the low fluence weld. [ABSTRACT FROM AUTHOR]

In this study, the effect of nitrogen on microstructural evolution and Charpy impact energy of CoCrFeMnNi high-entropy alloy (HEA) was investigated, and the corresponding fracture mechanism was revealed. Nitrogen atoms fully dissolved into the matrix and markedly increased the Charpy impact energy of 0.52 N alloy. The fracture morphologies of the 0 N and 0.52 N alloys were both featured with typical ductile fracture mode, while the serpentine glide morphology of 0.52 N alloy covered wider areas than that of 0 N alloy. Besides, the crack propagation path of 0 N alloy was relatively linear and flat, yet the zigzag crack propagation path was frequently deflected for 0.52 N alloy. The microstructure characterization indicated that the synergistic effect of the increased dislocation density and the more evenly distributed slip system contributed to the enhancement in impact toughness of 0.52 N alloy. • Contribution of nitrogen to impact toughness with relatively high strain rate of CoCrFeMnNi HEA was studied. • Nitrogen atoms fully dissolved in the matrix and no nitride was detected. • The essential reasons for improving the Charpy impact energy through nitrogen doping were revealed. • The increased dislocation density and more evenly distributed slip system improved impact toughness of 0.52 N alloy. [ABSTRACT FROM AUTHOR]

A comparison of both mechanical properties at different temperatures and resistance to creep related to steels 20MnCr5 and X10CrAlSi25 were investigated. In this sense, engineering stress-strain diagrams and creep curves are presented. Based on the mentioned diagrams, ultimate tensile strength, yield strength and modulus of elasticity as well as creep resistance may be compared. From the other hand, in accordance to measured Charpy impact energy, an assessment of fracture toughness was also made. In accordance with the experimental data, it is possible to say that structural steel 20MnCr5 (UTS: 20 °C / 600 °C = 562 MPa / 147 MPa; YS: 20 °C / 600 °C = 398 MPa / 141 MPa) and heat - resistant steel X10CrAlSi25 (UTS: 20 °C / 600 °C = 584 MPa / 487 MPa; YS: 20 °C / 600 °C = 132 MPa / 123 MPa) has have quite similar levels of the considered strengths at considered temperatures. Also, their resistance to creep is similar. [ABSTRACT FROM AUTHOR]

The 9Cr-1Mo steel used in fast breeder reactor is exposed to irradiation during service which severely affects the dynamic fracture resistance by increasing the ductile to brittle transition temperature (DBTT). Thus, even at room temperature, the steel can become brittle and prone to cracking. The microstructural features especially prior austenite grain size (PAGS), martensitic lath and packet size originating from prior processing routes has an effect on the toughness properties of 9Cr-1Mo steel, which is yet to be understood fully. In the present investigation, three different austenitizing temperatures (950 °C, 1025 °C and 1100 °C for 1 h) have been selected to vary the PAGS. Impact energy, lateral expansion, dynamic yield stress as the function of temperature has been estimated from Charpy impact tests carried out on normalized and tempered specimens. The results show lower DBTT for the samples reheated at 1025 °C followed by tempering. [ABSTRACT FROM AUTHOR]

An Al–TiC nanocomposite powder with different percentages of TiC nanoparticles, was synthesized via high energy ball milling. With increasing the TiC nanoparticles content, the crystallite size began to decrease, which led to an increase in the hardness of the produced nanocomposite. An Al–TiC laminated nanocomposite was then fabricated and the effect of process parameters on its Charpy impact energy (CIE) in both crack divider and crack arrester configurations was investigated. Comparison between the experimental results shows that for each of the crack divider and crack arrester configurations, the CIE of the laminated nanocomposite is much higher than that of monolithic one. We also reported an accurate estimate of the process parameters in order to maximize the Charpy impact energy in Al–TiC laminated nanocomposite. Accordingly, 99 datasets were collected from the experiments and then by a modeling algorithm called gene expression programing (GEP), a mathematical relation between the CIE and process parameters was developed. Afterwards by an optimization algorithm called Biogeography Based Optimization (BBO), the process parameters were optimized in order to achieve maximum CIE. Experiments were performed at the optimized parameters to prove the validity of the analysis which shows the potential application of these calculations and analysis in materials engineering. [ABSTRACT FROM AUTHOR]

Abstract: Starting from the fact that the experimental data are real data, and that the assessment of their values is of great importance in a design of the structure, this article seeks to draw attention to the designers of experimental data related to steel 20MnCr5 (1.7147, AISI 5120). In this sense, this paper presents the experimental results involving material ultimate tensile strength, yield strength, creep behavior, total fracture strain, reduction in the area as well as Charpy impact energy. All of the mentioned tests were conducted at room temperature and at elevated temperatures. Considerable tensile testing referring to determination of ultimate tensile strength as well as 0.2 offset yield strength resulted in engineering stress–strain diagrams, while those tensile testing regarding creep behavior resulted in creep curves. Also, modeling of material creep behavior using rheological models and an equation proposed by the authors can be found in this paper. Using Charpy impact energy tests, an assessment of fracture toughness was made. In addition to this, the paper presents a comparison of the material properties of 20MnCr5 steel with material properties of other similar (structural/constructional) steels. [Copyright &y& Elsevier]

Abstract: In order to provide a new possibility for improving the steel-making productivity by fabricating plain carbon steels containing high phosphorous (P), effects of microstructures on tensile and Charpy impact properties were investigated in this study. Nine plain carbon steels were fabricated by controlling the addition of P and boron (B), and isothermal or quench heat-treatments were conducted on these steels to make ferrite–bainite-based or martensite-based microstructures. The addition of B positively influenced the grain refinement and the formation of bainites, thereby leading to the increase in strength. The upper shelf energy (USE) decreased with increasing P content, while the energy transition temperature (ETT) increased, in all the steels. The B addition beneficially affected both the USE and ETT as the dimpled ductile fracture mode prevailed in the B-added steels. This was because B preferentially covered grain boundaries, which reduced the grain boundary segregation of P. Thus, it effectively suppressed the intergranular fracture due to the segregation of P. According to the fractographic results, the increased tendency of intergranular fracture mode was observable in the 20-ppm-B-added steels rather than in the 10-ppm-B-added steels. When an excess amount of B, e.g., 20ppm of B, was added, the severe segregation of B on grain boundaries occurred, and led to the precipitation of boro-carbides, which could act as intergranular crack initiation sites. [Copyright &y& Elsevier]

Abstract: In this study, toughness properties of a non-heat-treating cold-drawn bar were examined by Charpy impact test and fracture toughness test, and the toughness enhancement mechanisms were clarified in relation with microstructure. As the thickness of pearlite bands decreased after the cold drawing, the Charpy impact energy of the cold-drawn bar was higher than that of the as-rolled bar, which could be reasonably explained by the thin sheet toughening. On the other hand, thin pearlite bands negatively affected the fracture toughness because of the decreased spacing between crack or void initiation sites inside the fracture process zone in front of the pre-fatigued crack tip. The Charpy impact test data could also be correlated with the absorbed energy of the dynamic compressive test specimen whose orientation was matched with the hammer impact direction of the Charpy impact test, although the Charpy impact and dynamic compressive test specimens had a notched body and a smooth body, respectively. [Copyright &y& Elsevier]

Abstract: The purpose of this paper is to present the research results concerning S275JR (1.0044) steel material behavior loaded at room and elevated temperatures as well as result analysis in relation to its possible application. In this way, the data will be added to the existing data pool of considered material so as to be more readily available to other researchers and interested parties. Tensile testing of round specimens and Charpy impact testing of single edge notch bend specimens was conducted at different temperatures. On the basis of mentioned research, the following material properties were determined: ultimate tensile strength (σm ), 0.2% offset yield strength (σ 0.2), modulus of elasticity (E) and Charpy impact energy (CVN). Also, short-time creep behavior was examined. Test results are presented in the form of engineering stress–strain diagrams, the curves of the temperature dependence on material properties as well as creep curves. At the end of this paper, an assessment of fracture toughness based on the Charpy impact energy is given. [Copyright &y& Elsevier]